1. Field of the Invention
This invention relates to a catalyzer arrangement for an engine, and more particularly to an improved catalyzer arrangement that is suitable to an engine of an outboard motor.
2. Description of Related Art
A typical outboard motor includes an engine for powering a propulsion device. A protective cowling surrounds the engine. The engine and protective cowling together define a power head of the outboard motor. A driveshaft housing depends from the power head and supports a driveshaft that extends from a crankshaft of the engine. A lower unit depends from the driveshaft housing and carries a propulsion device, such as, for example, a propeller that is driven by the driveshaft through a propulsion shaft. The engine is provided with an exhaust system that discharges exhaust gases from the motor.
A typical exhaust system generally comprises three exhaust passages. The first passage is disposed within the engine or on the engine and within the protective cowling. The first passage leads exhaust gases away from the engine. The second passage is disposed within the driveshaft housing and the lower unit and guides the exhaust gases to the third passage. The second passage also silences exhaust noise by passing the exhaust gases through at least one expansion chamber. The third passage is defined within a hollow hub of the propeller and terminates at a discharge port formed at the end of the hub. Normally, an idle exhaust passage with an idle discharge port is provided in the driveshaft housing above the water line of the body of water that surrounds the outboard motor. The majority of the exhaust gasses are discharged to the body of water through the discharge port of the propeller hub, while the idle exhaust gasses are discharged to the atmosphere through the idle discharge port.
It is quite important for environmental concerns to remove hydrocarbons and the like from exhaust gases. For at least this reason, the exhaust gases often are purified with a catalyzer that is disposed within the exhaust system. The catalyzer includes components that chemically react with the exhaust gases in a manner that renders certain of the exhaust gas constituents substantially environmentally harmless. The larger the catalyzer is, the greater its efficiency is; however, because the engine is surrounded by the protective cowling, space is at a premium and limited areas are available for positioning the catalyzer. If the engine has multiple cylinder bores, properly positioning the catalyzer becomes more difficult. Moreover, if a large single catalyzer or small multiple catalyzers are used to treat exhaust gases coming from the respective cylinder bores, finding adequate space within the cramped confines of the cowling becomes very difficult.
In one arrangement, such as that disclosed by U.S. Pat. No. 5,239,825, a catalyzer arrangement for a multiple cylinder engine features a single catalyzer that is disposed in the first exhaust passage and sideward of the engine. Although the arrangement is compact, the catalyzer is somewhat bulky.
U.S. Pat. No. 5,378,180 discloses another arrangement in which a catalyzer is disposed also in the first exhaust passage but rearward of an engine. This type of arrangement, however, requires a large amount of space rearward of the engine. It is undesirable to expand the motor rearward because such a construction would make handling of the motor more difficult. Additionally, if the engine operates on a four-stroke combustion principle, a voluminous valve system is disposed in this space and consumes a majority of the available area.
U.S. Pat. Nos. 5,174,112 and 5,280,708 disclose further arrangements of catalyzers. The catalyzers in these patents are disposed in the second exhaust passages that are positioned within the driveshaft housing. Although a relatively large capacity is available with the catalyzer in this arrangement, the catalyzer is likely positioned proximate the water line. As is known, catalyzers can be fouled or shattered by contact with water. Accordingly, positioning the catalyzers proximate the water line is disadvantageous due to the possibility of water back flow through the exhaust system. Thus, catalyzers preferably are positioned well above the water line or the exhaust system preferably includes a shelter that can protect the catalyzers from water contact.
A need therefore exists for an improved catalyzer arrangement that does not require a large space within an outboard motor for furnishing a catalyzer that has a relatively large volume, and that does not substantially increase the likelihood that the catalyzer will be contacted by water.
In accordance with one aspect of the present invention, an internal combustion engine is provided for an outboard motor. The outboard motor has a protective cowling surrounding the engine. The engine comprises a cylinder body in which a plurality of cylinder bores are spaced apart from each other. An exhaust manifold gathers exhaust gases from the respective cylinder bores. An exhaust passage is coupled to the manifold and extends, at least in part, within a space defined between a side surface of the cylinder body and the protective cowling. A catalyzer is disposed in the exhaust passage.
In accordance with another aspect of the present invention, an exhaust gas purifying system is provided for an internal combustion engine. The engine has a side surface. The purifying system comprises an exhaust passage disposed on the side surface of the engine for catalytic exhaust treatment. The exhaust passage communicates with the engine through an inlet opening and an outlet opening. At least one catalyzer is disposed between the inlet and outlet openings.
In accordance with a further aspect of the present invention, an exhaust gas purifying system is provided for an internal combustion engine. The engine has a side surface. The purifying system comprises an exhaust passage disposed on the side surface of the engine for catalytic exhaust treatment. The exhaust passage includes a vertical section extending generally vertically along the side surface of the cylinder body. A catalyzer is disposed within the vertical section.